Rotary spark gap



Dec. 23, 1947. E. M. WILER ET AL ROTARY SPARK GAP Filed July 2, 1945 F I G. 2

INVENTOR. EDWARD M. WI LE RALPH R.HALLEN Fl 6. 3 By ATTORNEY' IGJ Patented Dec. 23, 1947 ROTARY SPARK GAP Edward M. Wiler, Belmar, N. J., and Ralph It. Hallcn, Fort Schuyler, N. Y.

Application July 2, 1943, Serial No. 493,280

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 9 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to us of any royalty thereon.

This invention relates to spark gaps, and more particularly to rotary spark gaps.

A spark gap may be used to key a transmitter for pulse-echo or other work. It is advantageous for some purposes to use a rotary spark gap in order to maintain a constant frequency pulse. Metal is dissipated or sputtered from the cathode of a spark gap, and a rotary spark gap cathode has the additional advantage that there are a considerable number of electrodes to distribute the loss. In order to further prolong the useful life of the rotary spark gap, it has been proposed to rotate the electrodes about their individual axes at the same time that they are revolved about the axis of the rotor.

Such a spark gap is disclosed in the patent to Irving Sager and Edward Wiler, Number 2325,7537, dated August 19, 1947, the application for which was copending herewith. The mechanism of the said spark gap is somewhat intricate in using a differential belt and pulley system together with a sun and planet gears in order to rotate the electrodes.

The primary object of the present invention is to generally improve rotary spark gaps of the socalled cage type. A more specific object is to simplify and cheapen the mechanical structure needed to produce the desired rotation of the electrode rods, and to eliminate interengaging parts which are subject to friction and wear.

We have fulfilled the foregoing objects by providing the electrode rods with disks, and subjecting portions of the said disks to the influence of stationary means, preferably magnetic poles, which tend to restrain the movement of the disks, and so to cause a slow rotation of the electrode rods relative to the rotor as the rotor spins.

To accomplish the foregoing general objects, and other more specific objects which will hereinafter appear, our invention resides in the rotary spark gap elements and their relation one to the other as are hereinafter more particularly described in the specification and sought to be defined in the claims. The specification is accompanied by a drawing in which Figure 1 is a plan view of a rotary spark gap embodying features of our invention;

Figure 2 is a front elevation of the same;

Figure 3 is a transverse section taken approximately in the plane of the line 3-3 of Figure 1; and

Figure 4 shows the configuration of one particular form of permanent field magnet employed in the present spark gap.

Referring to the drawing, the spark gap comprises a stationary electrode l2, cooperating with a so-called cage type rotor generally designated R, driven by a motor 20. Electrodes 26 are rotatably carried by the rotor R, and are provided with disks 30 which move between braking means, preferably the poles of a stationarily-mounted permanent field magnet M. We prefer to make the disks of a non-ferrous, highly-conductive metal, and rely upon eddy current reaction. More specifically, the disks are made of copper or aluminum, and as they pass between the poles of the magnet, eddy currents are induced in the disks, which in turn set up a magnetic field tending to oppose the motion of the disks past the poles, This constitutes in effect a magnetic brake which restrains the outer portions of the disks somewhat, and thus causes a slight rotation of the electrodes relative to the rotor.

The rotor R is mounted on a preferably insulation shaft I4, one end of which is carried in a ball bearing mounted in a pedestal l6, and the other end of which receives and is rigidly connected to the shaft l8 of driving motor 20. For constant pulse frequency, the motor 20 is preferably a constant-speed motor, typically a synchronous motor.

The rotor is made up of spaced end disk 22 and 24, which carry a series of electrode rods 26 therebetween, said rods preferably being round rods made of a high-temperature metal, such as tungsten or molybdenum. These rods pass through the end disks 22 and 24 and are rotatably carried therein. In fact, the disks are preferably provided with small bushings of the oilless or selfliliobricating type, in which the rods 26 are rotata le.

It is convenient to make the disks 30 of appreciable diameter, but it is also convenient to have a considerable number of electrode rods in order to reduce the necessary rotative speed of the rotor for any desired pulse frequency. These apparently conflicting requirements may be reconciled by using an even number of electrode rods, and mounting disks on alternate rods at one end of the rotor, while the disks for the intermediate rods are mounted at the other end of the rotor. Specifically, in this case there are eight electrode rods spaced uniformly about the periphery of the rotor, four of which carry disks 30 at the end nearer the motor, while the intermediate four rods carry disks 32 at the end remote from the motor. Each of the electrode rods carries a collar 34 at the end remote from the 3 disk, the said rod being held against axial movement by the hub of the disk at one end and the collar at the other end. The collars 34 and also the hubs of the disks are preferably removably secured, as by the use of set screws, thus making it possible to renew the electrode rods.

The disks 3!] at one end of the rotor are acted upon by the field magnet M previously referred to, while the disks 32 at the other end of the rotor are acted upon by another similar field magnet M.

The field magnets may be of any desired form, but that here shown is a conventional magnet used for the brake in one known type of watthour meter. consists of a single steel bar 35 of rectangular cross section, said bar being bent to provide spaced poles at 38 and 4D. The magnet is supported by an angle bracket 42, which is made of a non-ferrous material such as brass. The disks move in longitudinal direction in the space bounded on one side by the poles 38 and 40, and bounded on the other side by the part 44. It will be understood that other forms of field magnet are used in watt-hour meters, some for example employing another air gap at the point 44, and any such standard field magnet construction may be used for the present purpose.

In the particular structure here shown, the rotor is made up of a generally tubular hub portion 46, having integrally-formed flanges 48, to which the end disks 2-2 and 24 of the rotor are secured. The tubular hub portion 46 includes an axial extension 50, having a flange 52 at its end. In the present case, the flanges 48 and 52 and the tubular portions 46 and 50 are all formed integrally, and are preferably made of a conductive metal, such as brass. The flange 52 acts as a slip ring for electrical connection to the outside circuit. This connection is made to a brush holder 54 mounted on the bearing pedestal I6 previously referred to. A brush 56, made for example of carbon, is slidably received in brush holder 54, and is urged into engagement with the slip ring 52 by means of a suitable compression spring inserted in back of the brush.

The stationary electrode I2 is preferably made of a rod of tungsten or other high-temperature metal. It is disposed parallel to the rotor electrodes and is secured at the end of a slide or plate 53, preferably made of brass. The plate 58 is carried at the upper end of an insulation post 69. It is preferably slotted as shown at 62 in Figure 1, thereby making it possible to adjust the dimension of the gap between the electrodes. External connection may be made to the stationary electrode in known fashion by using a soldering lug, not shown.

In the particular case here illustrated, the rotor shaft is carried on a single bearing, the motor 20 acting as the opposite end bearing. It will be understood, however, that if desired the rotor shaft may be mounted on spaced ball bearings and may be connected to the motor by means of a suitable flexible coupling, instead of the rigid connection here shown. The base and shaft are shown broken in Figures 1 and 2, because in practice the shaft is preferably lengthened in order to increase the breakdown insulation between the motor and the spark gap.

When connecting the spark gap in circuit, the rotor is preferably made the cathode, because the cathode is relatively rapidly dissipated com pared to the anode. The latter, however, is subject to some wear, though only a small fraction Referring to Figure 4, the magnet,

4 of the wear of the cathode. All of the electrodes may be replaced when worn, but the useful life of the electrodes before requiring replacement is greatly increased by the present invention.

It will be understood that only a very slight rotation of the electrodes is needed. In fact, a slight movement is better than a substantial movement in order to avoid any possibility of the same electrode surface being presented to the stationary electrode after each one or few rotations of the rotor. With the present arrangement we are readily able to produce a rotation of the electrodes of the order of only one or two R. P. M., while using a rotor speed of the order of 1800 to 3600 R. P. M. This advantage is in addition to the obvious one that the mechanism is devoid of gears or like contacting parts which are subject to wear.

It is believed that the construction and operation of our improved spark gap, as well as the advantages thereof, will be apparent from the foregoing detailed description. It will also be apparent that while we have shown and described our invention in a preferred form, many changes and modifications may be made in the structure disclosed without departing from the spirit of the invention, as sought to be defined in the following claims.

We claim:

1. A rotary spark gap comprising a, stationary electrode, a rotor including a plurality of electrode rods cooperating with the stationary electrode, a motor to drive the rotor, and additional means to rotate the rods relative to the rotor as they revolve about the axis of the rotor, said means including disks secured on the rods, and a stationary means so positioned as to restrain a portion of the disks as the said disks run past the stationary means,

2. A rotary spark gap comprising a stationary electrode, a rotor, said rotor including circular end disks with a plurality of round electrode rods extending in axial direction between the disks and spaced about the periphery of the disks, said rods acting as movable electrodes for cooperation with the stationary electrode, a motor to drive the rotor, and additional means to rotate the rods relative to the rotor as they revolve about the axis of the rotor, said means including disks secured on the rods, and a stationary means so positioned as to restrain the outer portion of the disks as they run past the stationary means.

3. A rotary spark gap comprising a stationary electrode, a rotor including a plurality of electrode rods cooperating with the stationary electrode, a motor to drive the rotor, and additional means to rotate the rods relative to the rotor as they revolve about the axis of the rotor, said means including metal disks secured on the rods, and a stationary magnet sopositioned that the disks run between the poles of the magnet as the rotor rotates.

4. A rotary spark gap comprising a stationary electrode, a rotor, said rotor including circular end disks with a plurality of round electrode rods extending in axial direction between the disks and spaced about the periphery of the disks, said rods acting as movable electrodes for cooperation with the stationary electrode, a. motor to drive the rotor, and additional means to rotate the rods relative to the rotor as they revolve about the axis of the rotor, said meansincluding meta-l disks secured on the rods, and a stationary magnet so positioned that the disks run between. the poles of the magnet as the rotor rotates.

5. A rotary spark gap comprising a stationary electrode, a rotor including a plurality of electrode rods cooperating with the stationary electrode, a motor to drive the rotor, and additional means to rotate the rods relative to the rotor as they revolve about the axis of the rotor, said means comprising a highly conductive non-ferrous metal disk secured to each of the electrode rods, and a stationary magnet so positioned that the outer portion of each of the disks runs between the poles of the magnet as the rotor rotates, the movement of said disk between the poles causing an eddy current flow which generates a magnetic field which opposes the movement of the disk past the magnet.

6. A rotary spark gap comprising a stationary electrode, a rotor, said rotor including circular end disks with a plurality of round electrode rods extending in axial direction between the disks and spaced about the periphery of the disks, said rods acting as movable electrodes for cooperation with the stationary electrode, a motor to drive the rotor, and additional means to rotate the rods relative to the rotor as they revolve about the axis of the rotor, said means comprising a highly conductive non-ferrous metal disk secured to each of the electrode rods, and a stationary magnet so positioned that the outer portion of each of the disks runs between the poles of the magnet as the rotor rotates, the movement of said disk between the poles causing an eddy current flow which generates a magnetic field which opposes the movement of the disk past the magnet.

'7. A rotary spark gap comprising a stationary electrode, a rotor, said rotor including circular end disks with an even number of round electrode rods extending in axial direction between the disks and spaced about the periphery of the disks, said rods acting as movable electrodes for cooperation with the stationary electrode, a motor to drive the rotor, alternate electrode rods having metal disks secured at one end of the rotor, the intermediate electrode rods having similar disks secured at the opposite end of the rotor, and stationary magnets mounted near the ends of the rotor in such position that the disks run between the poles of the magnets as the rotor rotates, whereby the rods are rotated relative to the rotor as they revolve about the axis of the rotor.

8. A rotary spark gap comprising a stationary electrode, a rotor, said rotor including circular end disks with an even number of round electrode rods extending in axial direction between the disks and spaced about the periphery of the disks, said rods acting as movable electrodes for cooperation with the stationary electrode, a motor to drive the rotor, alternate electrode rods having highly conductive non-ferrous metal disks secured at one end of the rotor, the intermediate electrode rods having similar disks secured at the opposite end of the rotor, and stationary magnets mounted near the ends of the rotor in such position that the disks run between the poles of the magnets as the rotor rotates, whereby the rods are rotated relative to the rotor as they revolve about the axis of the rotor.

9. In the operation of a rotary spark gap comprising a rotor carrying electrode rods with metal wheels, the method of prolonging the life of the electrode rods which includes successively subjecting the wheels on the electrode rods to the influence of a stationary magnetic field, successively inducing eddy currents into said wheels thus creating successive magnetic fields about said wheels opposing the stationary magnetic field and thereby slightly restraining the movement of the electrode rods and producing a slow rotation of the rods about their axes relative to the rotor as the rotor spins.

EDWARD M. WILER. RALPH R. HALLEN.

REFERENCES CITED UNITED STATES PATENTS Name Date Reppy Jan. 6, 1891 Number 

